During various phases of oil and gas operations it becomes necessary to control fluid communication between the inside of a well casing and the exterior of the well casing. A well casing and/or well liner will generally have one or more access points or holes positioned along its side. A movable door apparatus will have one or more complimentary openings. When an opening or “door” of such a movable door apparatus is moved into alignment with an access point of the well casing, inflow of materials, such as hydrocarbons exterior to the casing, into the interior or inside of the well casing is enabled. By moving the slidable doors out of alignment with openings in the well casing, inflow of materials is controlled. A shifting device, such as a well intervention tool, located within the well casing and acting under a force imposed by a tractor or under the force of an actuator, is used to shift the position of the slidable doors. The shifting device comprises shifter keys which are configured to engage the profile of the slidable doors. The keys may be independently movable. Once the profile of the slidable door is successfully engaged, the door can be moved uphole or downhole, as needed.